This invention relates to electronic switching devices, and more particularly to high and low level energy detection devices such as proximity switches.
Such energy detection devices typically have a sufficiently high input impedance so as not to bleed off the field potential of the object being measured. Such switches operate devices by merely being touched or coming within a certain proximity to an object having a predetermined potential with respect to the circuit ground of the switch. There are many disadvantages to existing FET proximity switch type devices. One such disadvantage is that in the typical such FET switch the FET must be biased all of the time in order to be operative. This consumes unnecessary power, even though the power consumed is relatively small. The consumption of any power requires a source, such as a battery or photocell, which further adds to the bulk and expense of the switch.
Furthermore, there is a need for an electronic switch which can be operated by and switch into alternating or direct current over a broad voltage range. Typically, such circuits have a relatively narrow operating voltage and current range for operation of the switch.